Query : 2017A&A...603A..94S

2017A&A...603A..94S - Astronomy and Astrophysics, volume 603A, 94-94 (2017/7-1)

Planar infall of CH3OH gas around Cepheus A HW2.


Abstract (from CDS):

Aims. In order to test the nature of an (accretion) disk in the vicinity of Cepheus A HW2, we measured the three-dimensional velocity field of the CH3OH maser spots, which are projected within 1000au of the HW2 object, with an accuracy on the order of 0.1km/s.
Methods. We made use of the European VLBI Network (EVN) to image the 6.7GHz CH3OH maser emission toward Cepheus A HW2 with 4.5 milliarcsec resolution (3au). We observed at three epochs spaced by one year between 2013 and 2015. During the last epoch, in mid-March 2015, we benefited from the newly deployed Sardinia Radio Telescope.
Results. We show that the CH3OH velocity vectors lie on a preferential plane for the gas motion with only small deviations of 12°±9° away from the plane. This plane is oriented at a position angle of 134° east of north, and inclined by 26° with the line of sight, closely matching the orientation of the previously reported disk-like structure. Knowing the orientation of the equatorial plane, we can reconstruct a face-on view of the CH3OH gas kinematics onto the plane. CH3OH maser emission is detected within a radius of 900au from HW2, and down to a radius of about 300au, the latter coincident with the extent of the dust emission at 0.9mm. The velocity field is dominated by an infall component of about 2km/s down to a radius of 300au, where a rotational component of 4km/s becomes dominant. We discuss the nature of this velocity field and the implications for the enclosed mass.
Conclusions. These findings directly support the interpretation that the high-density gas and dust emission that surrounds Cepheus A HW2 traces an accretion disk.

Abstract Copyright: © ESO, 2017

Journal keyword(s): ISM: kinematics and dynamics - masers - stars: formation - stars: individual: Cepheus A HW2 - stars: individual: Cepheus A HW2

Simbad objects: 6

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Number of rows : 6
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4115 2
2 NAME BL Lac BLL 22 02 43.2913536816 +42 16 39.979416792   15.66 14.72     ~ 2140 1
3 NAME Cepheus A SFR 22 56 17.9 +62 01 49           ~ 721 2
4 NAME Cep A HW 2 Y*O 22 56 17.9 +62 01 49           B0.5 212 0
5 ICRF J230241.3+640552 Bz? 23 02 41.31499697 +64 05 52.8488544           ~ 34 1
6 NAME III CEP ASSOC As* 23 04.2 +63 24           ~ 313 0

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